The objective of this research program is a comprehensive study of the roles of chemical carcinogens in the induction of mouse mamary neoplasms. The following areas are being investigated: 1) The neoplastic significance of ductal and alveolar hyperplasias occurring in carcinogen-treated mice, 2) the significance of endocrine and immunological changes occurring in carcinogen-treated mice, 3) the changes in chromatin patterns during spontaneous and carcinogen-induced mammary tumorigenesis, and 4) the possible activation of latent mammary tumor virus by chemical carcinogens using immunological and biochemical methodology.